Relative Humidity Isn't What You Think It Is

TL;DR

Humidity levels reported by weather apps are relative and depend on temperature, making them less useful for planning your day accurately.

Transcript

This episode is brought to you by the Music for Scientists album, now available on all streaming services. Click the link in the description to start listening. [♪ INTRO] If you’ve ever paid close attention to the humidity levels on your phone’s weather app, you might have noticed that they seem to make no sense. Like, in the summer, your app can s... Read More

Key Insights

• 😀 Relative humidity reported by weather apps is a relative measure that depends on temperature.
• 🥹 Warmer air can hold more moisture, making it feel more humid even at the same percentage of relative humidity.
• 😥 Dew point temperature indicates how saturated the air is with moisture and provides a better understanding of humidity comfort.
• 😥 Weather apps continue to use relative humidity out of historical convention, despite dew point temperature being a more useful measure.
• 😥 Dew point temperature around 10 degrees Celsius is generally comfortable, while higher values indicate more unpleasant humidity.
• 🥳 Understanding the relationship between temperature and humidity can help you plan your day more effectively.
• 😥 Instruments that measure relative humidity predate those for measuring dew point temperature.

Questions & Answers

Q: Why does relative humidity seem inconsistent between different temperature conditions?

Relative humidity is affected by temperature because warmer air can hold more moisture without condensing. Therefore, the same percentage of humidity can feel different at varying temperatures.

Q: What is dew point temperature, and why is it a more useful measure of humidity?

Dew point temperature is the temperature at which air becomes saturated with moisture, resulting in dew formation. It provides a consistent measure of moisture content, regardless of temperature.

Q: Why don't weather apps use dew point temperature instead of relative humidity?

Weather apps historically relied on instruments that measured relative humidity, which were more widely available and provided reliable measurements. As a result, the term stuck even though dew point temperature is a more accurate indicator of humidity comfort.

Q: What is a comfortable dew point temperature for most people?

Most people find a dew point temperature of around 10 degrees Celsius comfortable. Humidity becomes more unpleasant as the dew point temperature approaches 15 or 21 degrees.

Summary & Key Takeaways

• Many weather apps report relative humidity, which compares the amount of moisture in the air to its capacity but does not consider temperature.

• Temperature affects the ability of air to hold moisture, with warmer air holding more moisture and feeling stickier.

• Dew point temperature, which indicates complete saturation of air with moisture, is a more accurate measure of how humid it feels outside.